/*
 * Copyright (c) 1982, 1986, 1988, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)ip_input.c	8.2 (Berkeley) 1/4/94
 * ip_input.c,v 1.11 1994/11/16 10:17:08 jkh Exp
 */

/*
 * Changes and additions relating to SLiRP are
 * Copyright (c) 1995 Danny Gasparovski.
 *
 * Please read the file COPYRIGHT for the
 * terms and conditions of the copyright.
 */

#include "slirp/slirp.h"
#include "slirp/ip_icmp.h"
#include <stdint.h>

int ip_defttl;
struct ipstat ipstat;
struct ipq ipq;

/*
 * IP initialization: fill in IP protocol switch table.
 * All protocols not implemented in kernel go to raw IP protocol handler.
 */
void ip_init() {
        ipq.ip_link.next = ipq.ip_link.prev = &ipq.ip_link;
        ip_id = tt.tv_sec & 0xffff;
        udp_init();
        tcp_init();
        ip_defttl = IPDEFTTL;
}

/*
 * Ip input routine.  Checksum and byte swap header.  If fragmented
 * try to reassemble.  Process options.  Pass to next level.
 */
void ip_input(m) struct SLIRPmbuf *m;
{
        register struct ip *ip;
        u_int hlen;

        DEBUG_CALL("ip_input");
        DEBUG_ARG("m = %lx", (long)m);
        DEBUG_ARG("m_len = %d", m->m_len);

        ipstat.ips_total++;

        if (m->m_len < sizeof(struct ip)) {
                ipstat.ips_toosmall++;
                return;
        }

        ip = mtod(m, struct ip *);

        if (ip->ip_v != IPVERSION) {
                ipstat.ips_badvers++;
                goto bad;
        }

        hlen = ip->ip_hl << 2;
        if (hlen < sizeof(struct ip) || hlen > m->m_len) { /* min header length */
                ipstat.ips_badhlen++;                      /* or packet too short */
                goto bad;
        }

        /* keep ip header intact for ICMP reply
         * ip->ip_sum = cksum(m, hlen);
         * if (ip->ip_sum) {
         */
        if (cksum(m, hlen)) {
                ipstat.ips_badsum++;
                goto bad;
        }

        /*
         * Convert fields to host representation.
         */
        NTOHS(ip->ip_len);
        if (ip->ip_len < hlen) {
                ipstat.ips_badlen++;
                goto bad;
        }
        NTOHS(ip->ip_id);
        NTOHS(ip->ip_off);

        /*
         * Check that the amount of data in the buffers
         * is as at least much as the IP header would have us expect.
         * Trim SLIRPmbufs if longer than we expect.
         * Drop packet if shorter than we expect.
         */
        if (m->m_len < ip->ip_len) {
                ipstat.ips_tooshort++;
                goto bad;
        }
        /* Should drop packet if SLIRPmbuf too long? hmmm... */
        if (m->m_len > ip->ip_len)
                m_adj(m, ip->ip_len - m->m_len);

        /* check ip_ttl for a correct ICMP reply */
        if (ip->ip_ttl == 0 || ip->ip_ttl == 1) {
                icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, 0, "ttl");
                goto bad;
        }

        /*
         * Process options and, if not destined for us,
         * ship it on.  ip_dooptions returns 1 when an
         * error was detected (causing an icmp message
         * to be sent and the original packet to be freed).
         */
        /* We do no IP options */
        /*	if (hlen > sizeof (struct ip) && ip_dooptions(m))
         *		goto next;
         */
        /*
         * If offset or IP_MF are set, must reassemble.
         * Otherwise, nothing need be done.
         * (We could look in the reassembly queue to see
         * if the packet was previously fragmented,
         * but it's not worth the time; just let them time out.)
         *
         * XXX This should fail, don't fragment yet
         */
        if (ip->ip_off & ~IP_DF) {
                struct ipq *fp;
                struct qlink *l;
                /*
                 * Look for queue of fragments
                 * of this datagram.
                 */
                for (l = (struct qlink *)(ipq.ip_link.next); l != &ipq.ip_link; l = (struct qlink *)(l->next)) {
                        fp = container_of(l, struct ipq, ip_link);
                        if (ip->ip_id == fp->ipq_id && ip->ip_src.s_addr == fp->ipq_src.s_addr &&
                            ip->ip_dst.s_addr == fp->ipq_dst.s_addr && ip->ip_p == fp->ipq_p)
                                goto found;
                }
                fp = NULL;
        found:

                /*
                 * Adjust ip_len to not reflect header,
                 * set ip_mff if more fragments are expected,
                 * convert offset of this to bytes.
                 */
                ip->ip_len -= hlen;
                if (ip->ip_off & IP_MF)
                        ip->ip_tos |= 1;
                else
                        ip->ip_tos &= ~1;

                ip->ip_off <<= 3;

                /*
                 * If datagram marked as having more fragments
                 * or if this is not the first fragment,
                 * attempt reassembly; if it succeeds, proceed.
                 */
                if ((ip->ip_tos & 1) || ip->ip_off) {
                        ipstat.ips_fragments++;
                        ip = ip_reass(ip, fp);
                        if (ip == 0)
                                return;
                        ipstat.ips_reassembled++;
                        m = dtom(ip);
                } else if (fp)
                        ip_freef(fp);

        } else
                ip->ip_len -= hlen;

        /*
         * Switch out to protocol's input routine.
         */
        ipstat.ips_delivered++;
        switch (ip->ip_p) {
        case IPPROTO_TCP:
                tcp_input(m, hlen, (struct SLIRPsocket *)NULL);
                break;
        case IPPROTO_UDP:
                udp_input(m, hlen);
                break;
        case IPPROTO_ICMP:
                icmp_input(m, hlen);
                break;
        default:
                ipstat.ips_noproto++;
                m_free(m);
        }
        return;
bad:
        m_freem(m);
        return;
}

#define iptofrag(P) ((struct ipasfrag *)(((char *)(P)) - sizeof(struct qlink)))
#define fragtoip(P) ((struct ip *)(((char *)(P)) + sizeof(struct qlink)))

/*
 * Take incoming datagram fragment and try to
 * reassemble it into whole datagram.  If a chain for
 * reassembly of this datagram already exists, then it
 * is given as fp; otherwise have to make a chain.
 */
struct ip *ip_reass(struct ip *ip, struct ipq *fp) {
        register struct SLIRPmbuf *m = dtom(ip);
        register struct ipasfrag *q;
        int hlen = ip->ip_hl << 2;
        int i, next;

        DEBUG_CALL("ip_reass");
        DEBUG_ARG("ip = %lx", (long)ip);
        DEBUG_ARG("fp = %lx", (long)fp);
        DEBUG_ARG("m = %lx", (long)m);

        /*
         * Presence of header sizes in SLIRPmbufs
         * would confuse code below.
         * Fragment m_data is concatenated.
         */
        m->m_data += hlen;
        m->m_len -= hlen;

        /*
         * If first fragment to arrive, create a reassembly queue.
         */
        if (fp == 0) {
                struct SLIRPmbuf *t;
                if ((t = m_get()) == NULL)
                        goto dropfrag;
                fp = mtod(t, struct ipq *);
                insque(&fp->ip_link, &ipq.ip_link);
                fp->ipq_ttl = IPFRAGTTL;
                fp->ipq_p = ip->ip_p;
                fp->ipq_id = ip->ip_id;
                fp->frag_link.next = fp->frag_link.prev = &fp->frag_link;
                fp->ipq_src = ip->ip_src;
                fp->ipq_dst = ip->ip_dst;
                q = (struct ipasfrag *)fp;
                goto insert;
        }

        /*
         * Find a segment which begins after this one does.
         */
        for (q = (struct ipasfrag *)fp->frag_link.next; q != (struct ipasfrag *)&fp->frag_link;
             q = (struct ipasfrag *)(q->ipf_next)) {
                if (q->ipf_off > ip->ip_off)
                        break;
        }

        /*
         * If there is a preceding segment, it may provide some of
         * our data already.  If so, drop the data from the incoming
         * segment.  If it provides all of our data, drop us.
         */
        if (q->ipf_prev != &fp->frag_link) {
                struct ipasfrag *pq = (struct ipasfrag *)(q->ipf_prev);
                i = pq->ipf_off + pq->ipf_len - ip->ip_off;
                if (i > 0) {
                        if (i >= ip->ip_len)
                                goto dropfrag;
                        m_adj(dtom(ip), i);
                        ip->ip_off += i;
                        ip->ip_len -= i;
                }
        }

        /*
         * While we overlap succeeding segments trim them or,
         * if they are completely covered, dequeue them.
         */
        while (q != (struct ipasfrag *)&fp->frag_link && ip->ip_off + ip->ip_len > q->ipf_off) {
                i = (ip->ip_off + ip->ip_len) - q->ipf_off;
                if (i < q->ipf_len) {
                        q->ipf_len -= i;
                        q->ipf_off += i;
                        m_adj(dtom(q), i);
                        break;
                }
                q = (struct ipasfrag *)(q->ipf_next);
                m_freem(dtom(q->ipf_prev));
                ip_deq((struct ipasfrag *)(q->ipf_prev));
        }

insert:
        /*
         * Stick new segment in its place;
         * check for complete reassembly.
         */
        ip_enq(iptofrag(ip), (struct ipasfrag *)(q->ipf_prev));
        next = 0;
        for (q = (struct ipasfrag *)(fp->frag_link.next); q != (struct ipasfrag *)&fp->frag_link;
             q = (struct ipasfrag *)(q->ipf_next)) {
                if (q->ipf_off != next)
                        return 0;
                next += q->ipf_len;
        }
        if (((struct ipasfrag *)(q->ipf_prev))->ipf_tos & 1)
                return (0);

        /*
         * Reassembly is complete; concatenate fragments.
         */
        q = (struct ipasfrag *)(fp->frag_link.next);
        m = dtom(q);

        q = (struct ipasfrag *)q->ipf_next;
        while (q != (struct ipasfrag *)&fp->frag_link) {
                struct SLIRPmbuf *t = dtom(q);
                q = (struct ipasfrag *)q->ipf_next;
                m_cat(m, t);
        }

        /*
         * Create header for new ip packet by
         * modifying header of first packet;
         * dequeue and discard fragment reassembly header.
         * Make header visible.
         */
        q = (struct ipasfrag *)(fp->frag_link.next);

        /*
         * If the fragments concatenated to an SLIRPmbuf that's
         * bigger than the total size of the fragment, then and
         * m_ext buffer was alloced. But fp->ipq_next points to
         * the old buffer (in the SLIRPmbuf), so we must point ip
         * into the new buffer.
         */
        if (m->m_flags & M_EXT) {
                int delta;
                delta = (char *)ip - m->m_dat;
                q = (struct ipasfrag *)(m->m_ext + delta);
        }

        /* DEBUG_ARG("ip = %lx", (long)ip);
         * ip=(struct ipasfrag *)m->m_data; */

        ip = fragtoip(q);
        ip->ip_len = next;
        ip->ip_tos &= ~1;
        ip->ip_src = fp->ipq_src;
        ip->ip_dst = fp->ipq_dst;
        remque(&fp->ip_link);
        (void)m_free(dtom(fp));
        m->m_len += (ip->ip_hl << 2);
        m->m_data -= (ip->ip_hl << 2);

        return ip;

dropfrag:
        ipstat.ips_fragdropped++;
        m_freem(m);
        return (0);
}

/*
 * Free a fragment reassembly header and all
 * associated datagrams.
 */
void ip_freef(fp) struct ipq *fp;
{
        register struct ipasfrag *q, *p;

        for (q = (struct ipasfrag *)(fp->frag_link.next); q != (struct ipasfrag *)&fp->frag_link; q = p) {
                p = (struct ipasfrag *)(q->ipf_next);
                ip_deq(q);
                m_freem(dtom(q));
        }
        remque(&fp->ip_link);
        (void)m_free(dtom(fp));
}

/*
 * Put an ip fragment on a reassembly chain.
 * Like insque, but pointers in middle of structure.
 */
void ip_enq(p, prev) register struct ipasfrag *p, *prev;
{
        DEBUG_CALL("ip_enq");
        DEBUG_ARG("prev = %lx", (long)prev);
        p->ipf_prev = prev;
        p->ipf_next = prev->ipf_next;
        ((struct ipasfrag *)(prev->ipf_next))->ipf_prev = p;
        prev->ipf_next = p;
}

/*
 * To ip_enq as remque is to insque.
 */
void ip_deq(p) register struct ipasfrag *p;
{
        ((struct ipasfrag *)(p->ipf_prev))->ipf_next = p->ipf_next;
        ((struct ipasfrag *)(p->ipf_next))->ipf_prev = p->ipf_prev;
}

/*
 * IP timer processing;
 * if a timer expires on a reassembly
 * queue, discard it.
 */
void ip_slowtimo() {
        struct qlink *l;

        DEBUG_CALL("ip_slowtimo");

        l = (struct qlink *)(ipq.ip_link.next);

        if (l == 0)
                return;

        while (l != &ipq.ip_link) {
                struct ipq *fp = container_of(l, struct ipq, ip_link);
                l = (struct qlink *)(l->next);
                if (--fp->ipq_ttl == 0) {
                        ipstat.ips_fragtimeout++;
                        ip_freef(fp);
                }
        }
}

/*
 * Do option processing on a datagram,
 * possibly discarding it if bad options are encountered,
 * or forwarding it if source-routed.
 * Returns 1 if packet has been forwarded/freed,
 * 0 if the packet should be processed further.
 */

#ifdef notdef

int ip_dooptions(m) struct SLIRPmbuf *m;
{
        register struct ip *ip = mtod(m, struct ip *);
        register u_char *cp;
        register struct ip_timestamp *ipt;
        register struct in_ifaddr *ia;
        /*	int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0; */
        int opt, optlen, cnt, off, code, type, forward = 0;
        struct in_addr *sin, dst;
        typedef u_int32_t n_time;
        n_time ntime;

        dst = ip->ip_dst;
        cp = (u_char *)(ip + 1);
        cnt = (ip->ip_hl << 2) - sizeof(struct ip);
        for (; cnt > 0; cnt -= optlen, cp += optlen) {
                opt = cp[IPOPT_OPTVAL];
                if (opt == IPOPT_EOL)
                        break;
                if (opt == IPOPT_NOP)
                        optlen = 1;
                else {
                        optlen = cp[IPOPT_OLEN];
                        if (optlen <= 0 || optlen > cnt) {
                                code = &cp[IPOPT_OLEN] - (u_char *)ip;
                                goto bad;
                        }
                }
                switch (opt) {

                default:
                        break;

                /*
                 * Source routing with record.
                 * Find interface with current destination address.
                 * If none on this machine then drop if strictly routed,
                 * or do nothing if loosely routed.
                 * Record interface address and bring up next address
                 * component.  If strictly routed make sure next
                 * address is on directly accessible net.
                 */
                case IPOPT_LSRR:
                case IPOPT_SSRR:
                        if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
                                code = &cp[IPOPT_OFFSET] - (u_char *)ip;
                                goto bad;
                        }
                        ipaddr.sin_addr = ip->ip_dst;
                        ia = (struct in_ifaddr *)ifa_ifwithaddr((struct sockaddr *)&ipaddr);
                        if (ia == 0) {
                                if (opt == IPOPT_SSRR) {
                                        type = ICMP_UNREACH;
                                        code = ICMP_UNREACH_SRCFAIL;
                                        goto bad;
                                }
                                /*
                                 * Loose routing, and not at next destination
                                 * yet; nothing to do except forward.
                                 */
                                break;
                        }
                        off--;
                        / *0 origin * / if (off > optlen - sizeof(struct in_addr)) {
                                /*
                                 * End of source route.  Should be for us.
                                 */
                                save_rte(cp, ip->ip_src);
                                break;
                        }
                        /*
                         * locate outgoing interface
                         */
                        bcopy((SLIRPcaddr_t)(cp + off), (SLIRPcaddr_t)&ipaddr.sin_addr, sizeof(ipaddr.sin_addr));
                        if (opt == IPOPT_SSRR) {
#define INA struct in_ifaddr *
#define SA struct sockaddr *
                                if ((ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr)) == 0)
                                        ia = (INA)ifa_ifwithnet((SA)&ipaddr);
                        } else
                                ia = ip_rtaddr(ipaddr.sin_addr);
                        if (ia == 0) {
                                type = ICMP_UNREACH;
                                code = ICMP_UNREACH_SRCFAIL;
                                goto bad;
                        }
                        ip->ip_dst = ipaddr.sin_addr;
                        bcopy((SLIRPcaddr_t) & (IA_SIN(ia)->sin_addr), (SLIRPcaddr_t)(cp + off), sizeof(struct in_addr));
                        cp[IPOPT_OFFSET] += sizeof(struct in_addr);
                        /*
                         * Let ip_intr's mcast routing check handle mcast pkts
                         */
                        forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
                        break;

                case IPOPT_RR:
                        if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
                                code = &cp[IPOPT_OFFSET] - (u_char *)ip;
                                goto bad;
                        }
                        /*
                         * If no space remains, ignore.
                         */
                        off--;
                        *0 origin *if (off > optlen - sizeof(struct in_addr)) break;
                        bcopy((SLIRPcaddr_t)(&ip->ip_dst), (SLIRPcaddr_t)&ipaddr.sin_addr, sizeof(ipaddr.sin_addr));
                        /*
                         * locate outgoing interface; if we're the destination,
                         * use the incoming interface (should be same).
                         */
                        if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) == 0 && (ia = ip_rtaddr(ipaddr.sin_addr)) == 0) {
                                type = ICMP_UNREACH;
                                code = ICMP_UNREACH_HOST;
                                goto bad;
                        }
                        bcopy((SLIRPcaddr_t) & (IA_SIN(ia)->sin_addr), (SLIRPcaddr_t)(cp + off), sizeof(struct in_addr));
                        cp[IPOPT_OFFSET] += sizeof(struct in_addr);
                        break;

                case IPOPT_TS:
                        code = cp - (u_char *)ip;
                        ipt = (struct ip_timestamp *)cp;
                        if (ipt->ipt_len < 5)
                                goto bad;
                        if (ipt->ipt_ptr > ipt->ipt_len - sizeof(int32_t)) {
                                if (++ipt->ipt_oflw == 0)
                                        goto bad;
                                break;
                        }
                        sin = (struct in_addr *)(cp + ipt->ipt_ptr - 1);
                        switch (ipt->ipt_flg) {

                        case IPOPT_TS_TSONLY:
                                break;

                        case IPOPT_TS_TSANDADDR:
                                if (ipt->ipt_ptr + sizeof(n_time) + sizeof(struct in_addr) > ipt->ipt_len)
                                        goto bad;
                                ipaddr.sin_addr = dst;
                                ia = (INA)ifaof_ i f p foraddr((SA)&ipaddr, m->m_pkthdr.rcvif);
                                if (ia == 0)
                                        continue;
                                bcopy((SLIRPcaddr_t)&IA_SIN(ia)->sin_addr, (SLIRPcaddr_t)sin, sizeof(struct in_addr));
                                ipt->ipt_ptr += sizeof(struct in_addr);
                                break;

                        case IPOPT_TS_PRESPEC:
                                if (ipt->ipt_ptr + sizeof(n_time) + sizeof(struct in_addr) > ipt->ipt_len)
                                        goto bad;
                                bcopy((SLIRPcaddr_t)sin, (SLIRPcaddr_t)&ipaddr.sin_addr, sizeof(struct in_addr));
                                if (ifa_ifwithaddr((SA)&ipaddr) == 0)
                                        continue;
                                ipt->ipt_ptr += sizeof(struct in_addr);
                                break;

                        default:
                                goto bad;
                        }
                        ntime = iptime();
                        bcopy((SLIRPcaddr_t)&ntime, (SLIRPcaddr_t)cp + ipt->ipt_ptr - 1, sizeof(n_time));
                        ipt->ipt_ptr += sizeof(n_time);
                }
        }
        if (forward) {
                ip_forward(m, 1);
                return (1);
        }
}
}
return (0);
bad :
        /* ip->ip_len -= ip->ip_hl << 2;   XXX icmp_error adds in hdr length */

        /* Not yet */
        icmp_error(m, type, code, 0, 0);

ipstat.ips_badoptions++;
return (1);
}

#endif /* notdef */

/*
 * Strip out IP options, at higher
 * level protocol in the kernel.
 * Second argument is buffer to which options
 * will be moved, and return value is their length.
 * (XXX) should be deleted; last arg currently ignored.
 */
void ip_stripoptions(m, mopt) struct SLIRPmbuf *m;
struct SLIRPmbuf *mopt;
{
        register int i;
        struct ip *ip = mtod(m, struct ip *);
        register SLIRPcaddr_t opts;
        int olen;

        olen = (ip->ip_hl << 2) - sizeof(struct ip);
        opts = (SLIRPcaddr_t)(ip + 1);
        i = m->m_len - (sizeof(struct ip) + olen);
        memcpy(opts, opts + olen, (unsigned)i);
        m->m_len -= olen;

        ip->ip_hl = sizeof(struct ip) >> 2;
}
